U.S. Pat. No. 4,199,545 discloses a chemical reactor capable of carrying out selected chemical reactions at extremely high temperatures. The reactor includes a vertically disposed reactor tube made of a fabric of fibrous refractory material capable of being heated to temperatures at which it emits intense radiant energy. The reactor includes electrically resistive heating elements spaced about the reactor tube for heating a reaction zone of the tube. A heat shield surrounds the heating elements and the reactor tube for reflecting radiant energy toward the reaction zone.
In operation, reactants are dropped through the heated reaction zone of the reactor tube where they are heated to high temperatures by radiant energy emitted by the fabric wall of the reactor tube. In order to prevent reactants and reaction products from adhering to the wall of the reactor tube, a gas which is substantially transparent to radiant energy and preferably inert with respect to the heated wall material is caused to flow radially inwardly through the pores of the fabric of the reactor tube to form a protective fluid wall for the inner surface of the reactor tube.
The U.S. Pat. No. '545 patent discloses inlet assemblies for introducing liquid and solid reactants into the reaction zone of the reactor. The inlet assembly for solid reactants includes an inlet tube which extends into the reactor tube generally along an axis of the reactor tube. A feed exit end of the inlet tube is surrounded by a tubular shroud which assists in containing finely divided solid reactants certrally within the reactor tube. The inlet assembly for liquid reactants also includes an inlet tube which extends into the reactor tube generally along an axis of the reactor tube. A fogging nozzle is mounted on the end of the inlet tube to introduce liquid reactants into the reactor tube as a fog.
The feed exit ends of the inlet tubes for liquid and solid reactants in the reactor of the '545 patent are located adjacent to a prereaction zone of the reactor tube. The prereaction zone is located above the reaction zone and is generally shielded from direct heating by the heating elements. Consequently, the temperature of the prereaction zone is typically substantially lower than the temperature of the reaction zone. In a commercial embodiment of the reactor of the U.S. Pat. No. '545 patent, the wall of the reactor tube adjacent to the prereaction zone is made of a nonporous refractory material and is not protected by a fluid wall.
The inlet assemblies for the reactor of the U.S. Pat. No. '545 patent have given rise to a number of significant problems. Although the wall of the reactor tube adjacent to the prereaction zone is lower in temperature than the wall adjacent to the reaction zone, it is often sufficiently hot to melt many solid feed materials introduced into the reactor. Moreover, since the wall adjacent to the prereaction zone is not protected by a fluid wall in the commercial embodiment of the reactor, solid feed material discharged from the inlet tube frequently impinges upon the wall of the prereaction zone and melts to form a slag. The molten slag then runs down the wall of the reaction tube and disrupts the fluid wall adjacent the reaction zone. Moreover, the molten slag is often corrosive and frequently attacks the reactor tube material. Liquid reactants discharged from the fogging nozzle also frequently impinge upon the wall of the prereaction zone, where they tend to corrode the wall or decompose to form solid deposits which tend to choke off flow through the reactor tube.
The precise location of the feed exit for the inlet assembly of the commercial embodiment of the above reactor has also presented problems. Locating the inlet assembly feed exit close enough to the mouth of the reaction zone to prevent feed material from striking the wall of the prereaction zone may cause the exit of the inlet assembly, which was made of metal, to melt from exposure to the intense radiant energy from the adjacent reaction zone. Also, slag deposits formed from melting feed material may accumulate on the exit of the inlet assembly, and such slag deposits may deflect the feed material against the wall of the reactor tube, thereby disrupting the protective fluid wall. Furthermore, exposure of the inlet assembly to the intense radiant energy at the mouth of the reaction zone causes severe deterioration of the inlet assembly, thereby increasing reactor component replacement costs and reactor downtime.
The disadvantages of the prior art are overcome by the present invention, and an improved feed tube assembly is hereinafter disclosed which may be mounted at a preferred location within the reactor without encountering numerous problems associated with the prior art inlet assemblies.